KVM: Write protect the updated slot only when dirty logging is enabled (c972f3b1) · Commits · 戴 / test

Calling kvm_mmu_slot_remove_write_access() for a deleted slot does nothing but search for non-existent mmu pages which have mappings to that deleted memory; this is safe but a waste of time. Since we want to make the function rmap based in a later patch, in a manner which makes it unsafe to be called for a deleted slot, we makes the caller see if the slot is non-zero and being dirty logged. Reviewed-by:

Marcelo Tosatti <mtosatti@redhat.com> Signed-off-by:

Takuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp> Signed-off-by:

Gleb Natapov <gleb@redhat.com>

arch/x86/kvm/x86.c

+7 −1

Original line number	Diff line number	Diff line
		@@ -6897,6 +6897,12 @@ void kvm_arch_commit_memory_region(struct kvm *kvm,
		spin_lock(&kvm->mmu_lock);
		if (nr_mmu_pages)
		kvm_mmu_change_mmu_pages(kvm, nr_mmu_pages);
		/*
		* Write protect all pages for dirty logging.
		* Existing largepage mappings are destroyed here and new ones will
		* not be created until the end of the logging.
		*/
		if (npages && (mem->flags & KVM_MEM_LOG_DIRTY_PAGES))
		kvm_mmu_slot_remove_write_access(kvm, mem->slot);
		spin_unlock(&kvm->mmu_lock);
		/*

virt/kvm/kvm_main.c

+0 −1

Original line number	Diff line number	Diff line
		@@ -817,7 +817,6 @@ int __kvm_set_memory_region(struct kvm *kvm,
		if ((new.flags & KVM_MEM_LOG_DIRTY_PAGES) && !new.dirty_bitmap) {
		if (kvm_create_dirty_bitmap(&new) < 0)
		goto out_free;
		/* destroy any largepage mappings for dirty tracking */
		}

		if (!npages \|\| base_gfn != old.base_gfn) {

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